Please help...found fluid on lungs...cancer?

I have been having trouble breathing and chest pains, shortness of breath. Went to the doc. Asked for a chest xray. They just called me back...next day! Said they think I MIGHT have phnemonia to take anitibiotics and they will need to do further testing. Called my doc back and said that I need more information on what they see and what other possiblilities it could be. They won't talk to me and said I have to go in on Monday because it's not something they want to discuss over the phone!!! Please help I am in a panic!!!!! Do any of you have any information on the subject and do you know if it could be cancer even if it looks like fluid....any information....I am scared to death.